SCIENCE Q & A

THE NEW YORK TIMESPublished February 23, 2013 - 1:00am Last Updated February 23, 2013 - 9:33am

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Insect metabolism for many species slows drastically in the cold. (VICTORIA ROBERTS/NYT)

Diapause helps insects survive winter indoors

Q:How do stink bugs remain alert indoors through the winter while apparently doing without food or liquid?

A: Like many insects, the brown marmorated stink bug, Halyomorpha halys, has winter nutritional needs that are minimal and do not have to be met on a daily or even a weekly basis.

An invasive species from eastern Asia, the bug takes winter refuge in warm homes and may be roused from its usual winter inactivity by high heat.

Insect metabolism for many species slows drastically in the cold or in other unfavorable conditions, a shutdown called diapause.

As a 2007 article in The Journal of Insect Physiology explains, an insect usually feeds very little or not at all during diapause. Instead, it depends on energy reserves stored away before entering dormancy. These are predominantly fats, but other kinds of reserves are important to some species.

Researchers have found that interactions between stored nutrients and metabolism can influence whether an insect enters diapause and how long it remains dormant. How much of the stores get used up also has a big effect on fitness when it re-emerges. If a stink bug uses up too much of its reserves in waking up for winter activity, its long-term survival would presumably be affected. The bugs normally live six to eight months.

The physiological and biochemical mechanisms that regulate diapause are poorly understood but are suspected to include various chemical signals, like insulin levels.

Probiotics, cholesterol verdict not in yet

Q. Probiotics, the live bacteria found in yogurt and other foods, are known to improve digestive health. But cholesterol levels?

A. Some believe that the beneficial bacteria bind to cholesterol in the small intestine, preventing it from being absorbed into the bloodstream. But research has been mixed, and the studies reporting positive findings tend to be the ones financed by makers of probiotic supplements.

In a randomized study published in November, for example, researchers at McGill University recruited 127 people with high cholesterol and split them into two groups. One took a probiotic supplement twice a day for nine weeks, while a second group took a placebo. The probiotic group saw their total cholesterol drop by nine per cent and their LDL, or “bad,” cholesterol fall almost 12 per cent.

The study was financed by a probiotics company, Micropharma. Another company that makes probiotic products, MD Foods, has made similar research claims.

In a report in 2010, two researchers noted that while there was some evidence that probiotics might lower cholesterol, “controversial results” had surfaced. Among them were the findings of a British study in which 80 people were given probiotics for six weeks and then switched, later on, to a placebo. That study found no difference in cholesterol levels when the subjects took the supplement versus the dummy pills.